In elevator systems, calls are traditionally input using up/down buttons in the elevator waiting halls and car call buttons in the elevator cars. There is also an increasing trend to use so-called destination call systems, wherein each passenger inputs a personal destination floor call already in the waiting hall before entering an elevator car. The calls input by passengers are allocated in the elevator group control system by comparing different passenger route alternatives to each other and allocating the calls to the elevators so that the calls are served in a way that will optimize a characteristic or a combination of characteristics descriptive of the service provided by the elevator group. Allocation can be improved by applying in different traffic situations optimization criteria that are best suited for the traffic situation in question and/or by activating a so-called zoned operation mode, wherein the building floors are divided into zones comprising one or more floors and served by certain elevators of the elevator system.
These measures are designed to allow the elevator system to adapt itself to the prevailing traffic situation, such as e.g. up-peak traffic in the building. In order to forecast traffic situations or traffic types and traffic intensities, statistics are collected about traveling actions in the elevator system according to different times of the day and days of the week and, based on the statistical data thus collected, the traffic situation in the elevator system at each instant of time is forecast. There are also prior-art solutions wherein the times of arrival of passengers at the elevators serving them are forecast on the basis of the location of the call input device and control decisions are made on the basis of the forecasted time of arrival.
In today's elevator systems, elevators can be driven to floors by calls, by parking and congestion-mode return commands. Calls, regardless of whether they are car calls, destination calls, floor calls etc., are “strong commands” which are always executed. Parking commands are “weak commands” which are based on parameters or traffic statistics and which are used to move vacant elevators beforehand to floors from which passenger traffic is expected in the near future. Parking is a “weak command” because, when an actual call is received, the parking command is either transferred to another elevator or, if all the elevators have a call to be served, removed altogether. A congestion-mode return command is a “weak command” like parking, the purpose of which is to move elevators to a floor which at the moment is likely to be crowded by so many passengers that they can not be served by a single elevator.
The above-described prior-art solutions for forecasting future passenger traffic are based on parametrization, statistical data and calls already entered, and they are thus hardly capable of anticipating future passenger traffic at an early enough stage to allow optimal control decisions to be made. Traffic statistics are long-time averages, and consequently forecasts of future passenger traffic made on the basis of them are inaccurate, especially if there occur unexpected and fast changes in passenger traffic. There is therefore a need for solutions in which changes in passenger traffic can be anticipated in good time and an influence can be exerted on the elevator system's control decisions before the elevator system starts receiving calls caused by the forecasted passenger traffic and transporting passengers to their destination floors.